It's amazing, I've had the same anthropic dream a couple of times.
But it's spooky only in retrospect, when it happens it's more like: "Mph, I'm going to wake up because I've already woken up."
It lasts very briefly, but it's definitely something real.
This is a kind of "X files" thread.
Post experiences which spooked you, which made you doubt reality, mathematical or physical laws, your sanity, memory or perception. The more improbable the better, but no second-hand legends please, share only what you personally experienced. If you had the event later explained rationally please use rot13 to avoid spoilers.